1. Technical Field
This invention relates generally to an apparatus and method for saving power in a computer system such as a desktop or notebook type system. More particularly, the invention provides one or more "sleep" buttons which selectively power down different subsystems in a computer system on the basis of the status of various user-controlled consumer devices.
2. Related Information
Over the past several years, the electricity consumed by desktop computer systems has generally increased due to higher processor speeds, proliferation of peripherals, the use of larger displays, and other factors. Moreover, the increase in the number of computers has caused a corresponding increase in the total amount of electricity consumed. The increased electrical consumption generally harms the environment, thus prompting the Environmental Protection Agency to encourage computer makers to design computer systems with reduced power consumption. For portable computers such as so-called laptop or notebook style computers, power consumption is also a paramount concern.
Power saving features for general purpose computer systems such as desktop and notebook computer systems are well known. Some systems rely on a power management function which automatically transitions the computer to one or more power-saving states when no activities are detected. The power saving states are characterized by reduced power consumption and a reduced state of readiness. Such systems are typically designed on the assumption that a particular computer has a fixed configuration of components and peripherals. Accordingly, such techniques are not readily useful in systems which provide a wide variety of components having different power states of their own. Moreover, the user of such systems cannot directly control the power-down or re-awakening of the system since the transitions are typically predefined based on a rigid set of parameters.
Other systems provide a "suspend" mode which, when activated, slows down or stops the CPU clock, spins down the disk drive, sets the computer monitor in a "suspend" state, saves the state of various application programs, and stops most other peripheral functions. Thereafter, any interrupt such as a keyboard or modem interrupt will immediately re-activate the entire computer and suspended application programs. Such an approach still wastes more power than is necessary, because the entire system is either on or off, and a single modem interrupt can cause the full system to be powered up even though full power is not needed to service the function of interest.
Recently, personal computer systems have begun to converge with consumer devices such as televisions, radios, CD players, answering machines, and the like. These integrated systems have increased complexity, making it more difficult to apply conventional power management techniques.
As one example, when a television receiver is integrated into a personal computer (i.e., the television display shares the computer screen with application programs), conventional power management techniques are inappropriate. In particular, the display must remain energized to support the TV function even though other subsystems of the underlying computer may not be in use. Because conventional power management functions would automatically turn off the display when the underlying computer is not being used, such conventional methods would effectively shut down the TV function while it was in use. Conversely, leaving all peripherals powered up when only the TV function is used wastes power. Providing separate "off" switches for each device or combination of devices is too confusing and still does not solve many of the aforementioned problems. Consequently, a need exists for more sophisticated power saving techniques when consumer devices are integrated into personal computer system, such that the power management features have knowledge of the applications which are currently being used.